The peroxide 2,5-dimethylhexane-2,5-dihydroperoxide and its derivatives are a class of important industrial peroxide compounds. They are useful as initiators in free radical polymerization process. They are also useful peroxy compounds in visbreaking of polyolefins.
These peroxy compounds have been prepared by, for example, first reacting 2,5-dimethyl-2,5-dihydroxyhexane with 50% hydrogen peroxide in sulfuric acid to synthesize 2,5-dimethylhexane-2,5-dihydroperoxide followed by washing. This 2,5-dimethylhexane-2,5-dihydroperoxide is further reacted with disfunctional chloride, acyl chlorides, haloformate and related material, benzaledehyde, an aliphatic alcohol in an inorganic acid, and the like to prepare its diperoxy derivatives. See U.S. Pat. No. 3,117,166 (Jan. 7, 1964).
The shortcomings of the above-described two stage process are: (1) the 2,5-dimethylhexane-2,5-dihydroperoxide is isolated as solid which is acid- and heat-labile, specially when it is dry; (2) considerable time is consumed in the isolation step; and (3) the diperoxy derivatives, for example, 2,5-dimethyl-2,5-di(butylproxy) hexane, thus prepared are found to produce color and odor in visbreaking operations. First, the 2,5-dimethylhexane-2,5-dihydroperoxide, when treated with an acid to prepare its derivatives, is believed to undergo an acid-catalyzed heterolysis to products comprising acetone, ethylene glycol and other derivatives. Secondly, in order to isolate the 2,5-dimethylhexane-2,5-dihydroperoxide, a repeated washing step is required. Finally, the referenced process also produces, in addition to the desired conversion, 5- and 6-membered ring compounds, 2,5-2,2,5,5-tetramethyldihydrofuran and 3,3,6,6-tetramethyl-1,2-dioxacyclohexane, respectively. These cyclic compounds are formed because of the thermodynamically favored internal cyclization of 2,5-dimethyl-2,5-dihydroxy hexane.
It would therefore be a significant contribution to the art if a simplified process, which substantially improves the overall yield of the peroxy compounds and reduces the cyclic compounds contributing to undesired color and odor, is developed.